The present disclosure relates to a monitoring system for detecting an error of a harmonic filter in a high voltage direct current (HVDC) system, and a monitoring method thereof that may monitor a voltage error of a capacitor unit by the sensing of the voltage of the capacitor unit that configures a capacitor of the harmonic filter.
HVDC transmission is performed by converting alternating current (AC) power generated from a power station into direct current (DC) power to transmit the DC power and then re-converting the DC power into the AC power at a power receiving point to supply power. The HVDC transmission may enable efficient and economical power transmission through a voltage increase that is the advantage of AC power transmission, and overcome many limitations of the AC transmission.
The HVDC transmission needs the processes of converting the AC power into the DC power and converting the DC power into the AC power. In these processes, a harmonic wave is, however, generated by the characteristics of a switch and a load, and thus a harmonic filter is generally used in order to prevent an adverse effect by the harmonic wave.
The general configuration of such a harmonic filter is shown in FIG. 1.
Referring to FIG. 1, the harmonic filter includes a combination of one or more inductors, one or more capacitors, and one or more resistors. In addition, each of the one or more capacitors C1 to C3 may include a series/parallel combination of one or more capacitor units. The capacitor units may be connected in a series/parallel structure to configure a capacitor bank, which is shown in FIG. 2.
In the case where one or more of the capacitor units have a defect, a fault current by voltage imbalance may occur, and thus the capacitor bank and the harmonic filter have been typically protected by the method of detecting the fault current by using a leakage current detector.
However, since the typical method detects after an accident, i.e., after the fault current has occurred, there is a limitation in that there is a high possibility of failing to prevent the accident. Also, since the typical method detects the fault current, there is a limitation in that it is difficult to determine whether each of the capacitor units has an error.